Basic concepts

Requests and urls

Once launched, GBD WebSuite listens on ports 80/443 and processes GET and POST requests. Like a conventional webserver, GWS can serve static content, like html pages or images, but its main purpose is to provide dynamic map imagery and data. For dynamic requests, there’s a single endpoint (url), namely the _ (underscore). All requests to this endpoint are expected to contain the command (cmd) parameter. Additionally, all POST requests must be in JSON format.

Here a few examples of requests GBD WebSuite can handle:

Staic web requests

http://maps.my-server.com/images/smile.jpg

Dynamic GET requests (e.g. map imagery)

http://maps.my-server.com/_?cmd=mapHttpGetBbox&layer=london.metro&width=100&height=200&bbox=10,20,30,40

Dynamic POST request (e.g. search)

{
    "cmd":"searchRun",
    "params": {
        "projectUid": "london",
        "bbox": [10,20,30,40],
        "keyword": "queen"
    }
}

Dynamic GET urls can be modified using URL rewriting, so that this

http://maps.my-server.com/wms/london/metro

can be used instead of

http://maps.my-server.com/_?cmd=wmsHttpGetMap&project=london&layers=metro

Sites and projects

On the top level, GWS works with two types of entities: projects and sites. A project is roughly a map and a collection of settings related to that specific map. A site is a domain name, bound to authorization and routing rules.

In the above example, london is a project, metro is a layer configured for that project, while the domain name maps.my-server.com and the corresponding rewrite rule are taken from the site configuration.

Sites and projects are orthogonal concepts, and you can run the same project under multiple sites. For example, if you decide to change maps.my-server.com to e.g. gis.my-other-server.com this wouldn’t require any changes in the project london.

Actions

The set of commands (cmd in the above examples) is not fixed and is freely configurable. Commands are grouped into actions, you can configure available actions globally or on a per-project basis.

Maps, layers and sources

Every GBD WebSuite projects contains at least one map, which is a collection of layers. There are different types of layers (for example, “wms”, or “tile”). You can configure access rights, view properties (like an extent) and the metadata for the whole map and for each layer individually. A layer configuration typically contains instructions for the server how to transform the source data, for example

• reproject the data

• convert the imagery from WMS into tiles and vice versa

• reformat feature data

• apply custom styles to features

Pluggable architecture

Almost all GBD WebSuite features are implemented as plugins. We have plugins for these types of objects

actions	Server actions
authorization providers	Handle authorization and authentication
database providers	Database connections
search provides	Handle fulltext and attribute search
layers	Map layers
sources	Geodata sources for maps
print templates	Various print template formats

Pluggable objects in the configuration are identifed by their type property.

Configuration files and objects

GBD WebSuite supports several configuration formats:

• json, in which case the config file name must end with config.json

• yaml (config.yaml). We use json in these docs, but you can always use yaml with the same structure if you like it more

• python (config.py). Complex, repetitve or highly dynamic configurations can be also written in straight python. Your python config script must contain a function called config() returning a dict with the same structure as JSON. Note that your config module is executed inside the container, so it must be compatible with Python 3.6.

Configuration starts with the main config file (GWS_CONFIG), which can include other config files for projects and project groups. Once all files are read and parsed, all configured objects are assembled into a large “tree”, with the Application object being the root node. Here’s an example of such a tree

Application
|
|-- auth options
|-- server options
|-- web options
|
\-- projects
    |
    |-- First project
    |   |-- project options
    |   \-- Map
    |       |-- First layer
    |       \-- Second layer
    |
    \-- Second project
       |-- project options
       \-- Map
           \-- Layer group
               \-- Sub-layer

Most configuration options are inheritable, that means, when the system looks for some property for a layer, and it’s not configured explicitly, then the parent layer is consulted, then the map, then the containing project and finally the root Application.